Semi-supervised kernels via convex optimization with order constraints

An input gas stream containing SO2 is continuously treated in order to remove a substantial portion of the SO2 therefrom by the steps of: (a) scrubbing the input gas stream with an aqueous absorbent containing an alkaline reagent; (b) treating the resulting rich absorbent stream with a reducing agent at conditions selected to convert the sulfite compound contained therein to the corresponding thiosulfate compound; (c) reacting the resulting thiosulfate compound with carbon monixide at reduction conditions selected to produce the corresponding sulfide compound; (d) stripping hydrogan sulfide from the resulting solution to form a regenerated aqueous absorbent stream; and, thereafter, (e) passing at least a portion of the regenerated absorbent stream to the scrubbing step.